Roon certainly supports multichannel over USB when the core is connected directly to the DAC, and I believe when Roon Bridge is used on a Mac or Windows PC.
@john commented in a 2018 post that Linux based endpoints had trouble passing multichannel via USB – Multichannel USB DAC on Linux endpoint - "Transport: failed to initialize the audio device" error. There hasn’t been much recent discussion of multichannel USB that I can find.
Does anyone know whether multichannel USB works when the endpoint is running Ropieee?